Hi, i want to fit an RCBO onto my consumer unit for socket protection.There wasnt any instructions with it and all i have coming out of the back is a long black neutral cable and the white earth.I presumably connect the lives straight in but what about the neutrals? do they all connect to the fuseboard with the long neutral cable?

As I am sure you must have read, touching wiring in Con. unit is not allowed except by registered part p electrician.
For information though
assuming you have the right make & type to fit your C.U., it should have an entry for live busbar where old mcb was, at the other end will be two connections one marked for live(s) formerly fitted to mcb u r removing. there will be also a neutral term. which is to take the circuit neutral(s) which will be at the moment connected to the neutral term rail, the flying neutral lead goes to the hole in the rail left by the circuit neutrals u moved to the rcbo. .
the white earth wire goes to the earth rail in the same term as your circuit earth(s)
if this is not !00% clear DON'T TRY IT YOURSELF!
apart from the legal position you can cause many probs. moving wires around.
stay lucky,Sparx

DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!